Note before I start, yes, I am flying a big banner in my sig... one of those things
My opinion is this: Sigs should be limited to a very short number of characters, no images, no flash, no "nothing else". If you can't say it in one line, don't say it at all.
sig whoring has turned what was a somewhat useful board into a hellish playpen filled with surfers and college students trying to earn beer money. It is truly sad.
Alex